The invention relates to a method and chimney type apparatus for reducing the emission of solid particles which are generated, for example, when the charge of a horizontal chamber type coking furnace is discharged from the coking furnace for the subsequent quenching operation. In such a discharge operation the coking cake collapses as it is pushed into the quenching wagon, whereby the mixture of hot air, gas and solid dust particles forming above the collapsing coke cake is pulled as a heat convection current substantially vertically upwardly. For environmental reasons this particle laden heat convection current must be isolated from the atmosphere at least until the solid dust particles have been substantially cleaned out of the heat convection current or flow. Such cleaning may be accomplished in that the thermal lift or heat convection current is utilized in channelizing the mixture into a substantially vertically upwardly directed flow which is exposed to a liquid showering capable of binding or taking up the solid particle components of the flow. The invention is also directed to a chimney type apparatus for performing such a cleaning method.
It is known to use a so-called pressing machine for discharging a charge of coke from a horizontal chamber coking oven or furnace. The pressing machine presses the coke cake into a coke guide carriage which guides the coke cake into a quenching wagon or quencher car which transports the hot coke material to a quenching tower where the quenching is performed by means of water added to the hot coke material. During the pressing out operation when the quencher car is being loaded a strong thermal upwind is generated due to the high temperature difference between the coke cake as it is being pressed out of the coking chamber and the surrounding air. This strong thermal upwind vigorously entrains the dust particles which are liberated by the collapse of the coke cake, and the gases which are generated by an immediately occurring partial combustion. This upwind of a mixture of hot air and gases, as well as dust is clearly visible as a substantial dust output of prior art quenching systems. When, after completion of the pressing out operation, the coke has settled in the quenching car, and the loose, floatable dust particles have been carried off or whirled off so to speak in said upwind, no further coke dust emissions may be observed, except for the emissions resulting from the burn-off waste.
It is known to shower the collapsing coke cake with water by means of a showering device installed directly on the coke guide carriage in order to suppress the emission of coke dust. However, the coke guide carriage is not equipped with any devices for removing the solid particles bound to water droplets. Therefore, the emissions are precipitated in a zone more or less removed from the source of emission. However, it is an advantage of the just described direct showering of the coke with the water that the visual impression of the discharging materials is somewhat improved because the steam that is formed by the evaporating water envelopes the gray, solid particle laden cloud, thereby covering it with its lighter color. An actual reduction of the emission of solid particles cannot be achieved by this prior art method. However, the range of dust precipitation around the source of emission may be reduced in this manner.
However, the advantage of reducing the precipitation range which is achieved by the above described prior art method, must be compared with the substantial disadvantages which become primarily apparent in the form of substantial corrosion phenomena because the generated steam or vapor is capable of reducing the sulfur present in the high temperature coke. The predominant mass or proportion of such sulfur is organically bound in the carbon compound. However, the reduced sulfur makes the condensate formed from the vapor "acidic". Thus, the acidic condensate causes the corrosion of all metallic structural components of the coking furnace and of the plant.
Further, in the direct showering method the solid particles are rinsed into the rail track of the quenching car, whereby the drainage system is clogged and seepage of surface water into the ground is prevented. Thus, for example during a rainfall, the rail track system becomes flooded. It has been observed that such flooding water may even cause damage to the concrete structural components of the coking furnace plant.
German Patent Publication (DE-OS) No. 2,900,079 corresponding to U.S. Pat. No. 282,068, issued Aug. 4, 1981 discloses a method and apparatus for discharging the coke from a coking oven chamber with but little emission of solid particles in order to avoid the above described disadvantages. The disclosure of said German Patent Publication further intends to avoid in addition to the dust emission also an undesirable steam generation. According to this prior art a movable hood is arranged above the quenching car. The coke is sprayed with water from nozzles under the hood and the steam generated in the hood including any possibly present infiltrated air are sucked out of the hood or the steam is condensated in the hood. The water spraying of the hot coke is supposed to take place primarily in the lower zone of the hood so that necessarily substantial quantities of steam are generated in addition to the air infiltration. Such generated steam quantities and infiltrated air quantities must be sucked off and condensed.
Thus, such a device for performing this showering or spraying method is at least as expensive as extensive hood or hall systems in which the dust and gas laden air is entrapped, sucked off, and cleaned.
German Patent (DE-PS) No. 1,771,506 discloses a device constructed for entrapping the dust quantity produced during the pressing out of a coke charge from a horizontal chamber oven by means of a trapping hood. The so entrapped air carrying the dust is washed and then discharged into the atmosphere. For this purpose German Pat. No. 1,771,506 discloses a coke cake guide carriage which is equipped with said entrapping hood for the emitted dust and with suction devices as well as with washing equipment for the dust laden air. In this prior art system a discharge flue is arranged above the entrapping hood. The flue has a vertical central axis which is displaced relative to the entrapping hood. The flue is further equipped with sets of baffle means and with showering or spraying devices. A transition member is arranged between the entrapping hood and the discharge flue. The transition member has a cross-section which corresponds to the cross-section of the discharge flue and which is approximately half as large as the lower hood opening.
The just described prior art system disclosed in German Pat. No. 1,771,506 has the significant disadvantage that it is not possible to sufficiently prevent a contact between the washing liquid and the coke as it is being pressed out. This contact between the coked material as it is being pressed out and the washing liquid causes a sulfur emission. This is so because in high temperature coke the sulfur component is primarily present in an organic compound. Thus, if the coke comes into contact with water a water gas reaction is unavoidable, whereby the generated hydrogen is in a molecular state, that is in the nascent state which is capable of reducing the sulfur out of its carbon compound.
Another disadvantage of the just described system according to German Pat. No. 1,771,506 is seen in that the discharge flue is arranged with its central longitudinal axis in a displaced position relative to the catching hood. This position enforces a detour of the air gas dust mixture which prevents an optimal utilization of the thermal convection current generated by the pressing operation. Further, the direct spraying of the air gas dust mixture in countercurrent flow from the top downwardly impedes the thermal upwind or heat convection upward flow.
Summarizing the prior art, it may be said that all known systems for reducing the emission during the pressing out operation of a coke charge out of a horizontal chamber furnace are not only very expensive and involved, thereby increasing the production costs of the coke substantially, they also are unsatisfactory in their function. Besides, such prior art systems required for performing these known methods may be employed and operated only with a very high additional expense due to the frequent lack of space and due to furnace foundation structures which are all too often inadequate for the additional equipment.